Definition of “permutation”

noun

1. mathematics 
   1. an ordered arrangement of the numbers, terms, etc, of a set into specified groups  ⇒ the permutations of a, b, and c, taken two at a time, are ab, ba, ac, ca, bc, cb 
   2. a group formed in this way. The number of permutations of a group formed in this way. The number of permutations of n  objects taken a group formed in this way. The number of permutations of objects taken r  at a time is a group formed in this way. The number of permutations of objects taken at a time is n !/(a group formed in this way. The number of permutations of objects taken at a time is !/(n –a group formed in this way. The number of permutations of objects taken at a time is !/(–r)! nPrCompare combination (sense 6)
2. a combination of items made by reordering
3. an alteration; transformation
4. a fixed combination for selections of results on football pools perm